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Skin Radiation therapy > Genitourinary Brachy > Flashcards

Genitourinary Brachy Flashcards

1
Q

What must first be done in order to perform penile bratty?

A 
patient must be circumsiced 
allows for more accurate tumour extension
allows for follow up
reduces morbidity
reduces tumour volume
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2
Q

indications for penile brachy

A
  1. early stage disease
  2. Tumour <4cm
  3. less than 1cm invasion of the corpora cavernosum
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3
Q

technique for penile brachy

A

patient is catheterized under anesthetic
implant is usually with 2 plane with 1-1.5cm separations
dose is prescribed to 60Gy with a dose rate of .4-.5Gy/hrusing PDR foam protection and lead shielding for gonads and skin is done

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4
Q

complications penile bratty

A 
urethral stricture
ulceration 
necrosis
pain 
edema
impotence
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5
Q

PSA levels considered low mid and high risk

A

low <10
mid 11-20
high >20

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6
Q

gleason score low mid and high risk

A

low -<7
mid7-10
high >10

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7
Q

low mid and high risk Tlevel prostate cancer

A

low below T2a
mid T2b or T2c
highT3 and T4

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8
Q

indications for permanent LDR bratty in prostate cancer

A

alone in patients with low and mid risk T1 and T2 tumours

in combination with EBRT in mid and high risk patients

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9
Q

indications for temporary high dose rate (HDR) BRACHY PROSTATE cancer

A

in combination with mid and high risk patients

for patients with bratty alone for patients with low risk of extra capsular or seminal vesicle invasion

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10
Q

contraindications to prostate brachy

A
  1. previous TURP (transurethral resection of the prostate is now used more often than originally. now patients can have brachy post turp after a year
  2. urinary outflow restriction as it predicts a greater risk for complications flow rate of <15ml/s
  3. gland size upper limit is 50ml in many centres
  4. INABILITY TO UNDERGO ANESTHESIA
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11
Q

what type if bratty can cover a larger volume?

A

HDR can cover a larger volume than LDR

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12
Q

What sources are used for LDR brachy

A

I-125

Pd-103

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13
Q

most frequently used seed implant for LDR brachy (prostate)

A

I-125

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14
Q

energy and half life of I-125

A

25kev and half life 59.4 days

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15
Q

half life and energy of Pd-103

A

27kev and half life of 17 days

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16
Q

LDR brachy procedures (2) prostate

A
  1. conventional 2stage technique with initial volume study followed by seed implantation
  2. single stage technique including definition of CTV and interactive planning during seed preparation
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17
Q

target volume of LDR brachy (margins) prostate

A

target volume is typically the whole prostate plus a margin of 2-3mm

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18
Q

density and activity of seeds prostate brachy

A

activity is usually .4mCi / seed density of 2.5 seeds/ cm3

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19
Q

CTV

A

2-3mm outside the prostate capsule

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20
Q

DVH :CTV
V100
Urethra D 10, D30
Rectum

A 
CTV d90 (dose received by 90% of target volume) should be 100% prescription dose
V100:target volume receives prescription should get at least 95% prescription isodose
Urethra D10 (dose received by 10% of urethra) should be less than 150% prescription isodose
Urethra D30 (dose received by 30% of the urethra) should be less than 130% of the isodose
Rectum D2cc (dose received by 2cm 3 of the rectum) should be less than 100% of the prescription dose
21
Q

volume definition of prostate brachy

A

before implantation, TRUS is done in lithotomy position attached to the TRUS is a template the coordinates of the template are transposed onto the US on single step dosimetry stepper position will be fed to the computer so the position of the seeds can be planned with real time reconstruction of implant dosimetry .
The prostate is positioned so that is central in the template, urethra in the middled row.
Serial ultrasounds are taken from base to apex at 5mm intervals on each section the prostate capsule is outlined and info input into planning computer to calculate # and position of seeds, OAR, urethra and anterior rectal wall will also be defined

22
Q

how many needles and seeds are typical for a 40-50ml prostate

A

25-30 needles

80-100 seeds

23
Q

implantation of source

A

a 20cm long 18 gauge needle is inserted through the template the position of the needle at depth is determined by TRUS plane at the distance from the base plane then guiding needle into x and y coordinates until it reaches the plane at the correct depth the seeds are then inserted using a MICK applicator or through preloaded strands

24
Q

single step vs dual step planning procedure for implantation of sources

A

single step- the position of each seed within the volume is recorded and fed back to planning software building up the isodoses
the single step process has a better CTV coverage than the dual step process as 2 step relies on reproducing patient set-up between the volume study and implantation with precise reconstruction of the plan during implantation

25
Q

Does single or dual step planning procedure have better coverage of the CTV

A

Single step

26
Q

oerscription dose of I-125 goal

A

aim is to deliver minimum peripheral dose of 145Gy plus a margin of 2-3mm about 40-60% of volume will get 50% more than prescribed dose 220Gy and 20% will get 200% of the dose 290Gy

27
Q

dose for I-125 seed bratty as a boost after 50Gy ebrt

A

after 50Gy EBRT the I-125 seed dose is 110Gy

28
Q

Dose delivered by Pd-103 alone and after EBRT boost

A

alone-125Gy and ad a boost after EBRT 100Gy

29
Q

Radiobiology for I-125 vs Pd-103

A

I125 has isodose of 7.7cGyh dose falls with half life of 59.4 days dose rapidly accumulates after the first few weeks of implantation then rapidly falls off
Pd-103 has a higher dose rate but falls off quickly then side effects reach a peak sooner and settle quicker than for I-125

30
Q

post implant care for prostate brachy

A

initiative and obstructive symptoms occur and are aided by alpha blockers, pain on urination is helped by anti-inflammatory drugs, perineal bruising can be helped by ice packs, post implant antibiotics for 7-10 days are recomended

31
Q

Benign PSA bounce

A

one or 2 PSA increases may be followed by a slow fall in PSA

32
Q

do patients who have a gradual or quick PSA decrease fare better?

A

slow fall is better

33
Q

Target dosimetry parameters for a good implant

A

CTV
V100 should be >90%
D90 is at least = to prescribed dose of 145Gy

34
Q

most common type of biochemical failure after LDR brachy

A

when the PSA reaches a level >2ng ml-1 above the post implant nadir (lowest PSA level)

35
Q

side effects LDR brachy

A

urinary bowel and sexual function

36
Q

urinary side effects LDR

A

NEARLY ALL PATIENTS GET TEMPORARY URETHRITIS it can last 2-3 weeks to many months post implant
urinary retention can occur 2 weeks post implant the risk is higher for patients with large prostates this can be amended by categorization most patients use the caterer for 3-4 weeks

37
Q

rectal complications of LDR

A

proctitis, intermittent rectal bleeding and some discomfort this settles within a year

38
Q

sexual function side effects of LDR

A

MOST patients have ED before brachy and 30-40% of patients who don’t have ED will become impotent within 1-2 years post brachy the risk is higher for older men compared to younger men. The use of phosphodiesterase inhibitors are used

39
Q

who should avoid being near someone who had a LDR IMPLANT? HOW LONG SHOULD THEY STAY AWAY FROM these patients?

A

close contact <1m with young kids and pregnant women should be avoided for 2 months following implant avoid cremation 2 years post implant

40
Q

Difference between LDR and HDR for prostate brachy

A
  • HDR dosimetry is done after the implant applicators are placed, LDR the dosimetry is done and then the applicators are placed
  • larger volumes can be implanted with HDR
  • HDR brachy allows for larger dose /fx if prostate has a low alpha/beta ratio this is advantageous for HDR brachy
41
Q

Indications forHDR prostate brachhy

A

is mostly used for a boost after EBRT but is currently being looked at as a solo therapy

42
Q

HDR implant procedure for prostate

A

patient is in lithotomy position and has spinal or general anesthetic
urinary caterer is inserted
a rigid or flexible template is placed to help fixate the applicators to the perineal skin
HDR after loading applicators are placed within the prostate using TRUS applicators may be hollow needles or flexible plastic catheters
caterers can be inserted in 1 of 2 ways: peripheral weight with catheters around the periphery of the gland with a small # centrally OR individual needles placed for localized boosting
after completing the implant imaging is done and implant is reconstructed with 3d planning system, dosimetry is based on dwell times
CTV is defined on MRI and CT ctv2 is used in some centres encompasses the lobes of the prostate which will get a higher dose
Treatment delivery follows in the HDR after loading room
QA ensures cathéters don’t move between fractions
On completion of Tx catheters are removed
indwelling catheter will also be removed

43
Q

CTV in HDR prostate

A

CTV is the prostate capsule and the PTV is the CTV+2-3mm in each direction seminal vesicles may also be included in CTV if needed CTV2 is sometimes used in some centres and they encompass the peripheral lobes of the prostate

44
Q

OARS in HDR prostate brachy

A

urethra and anterior rectal wall

45
Q

HDR dosages what EBRT dose is given first

A 
EBRT in 45/25 followed by HDR bratty doses of 
6Gy x3
8.5Gyx2
11Gyx2
15Gyx2
46
Q

HDR dose if brachy is given alone

A

most commonly is 34-36Gy /4Fx

also: 31.5Gy/3 or 26Gy/2fx

47
Q

acute side effects from HDR bratty

A 
perineal bruising (goes away within a few days) occurs in almost every patient
Dysuria occurs for a few days after tx but doesn't last as long as with LDR
Proctitis with + frequency and urgency will persist for a few weeks after brachy
48
Q

late effects of HDR bratty

A

urethral stenosis occurs n 7% of patients late radiation proctitis and ED can also occur

Skin Radiation therapy (40 decks)

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